U.S. patent number 4,031,795 [Application Number 05/588,627] was granted by the patent office on 1977-06-28 for tone signal modulation system.
This patent grant is currently assigned to D. H. Baldwin Company. Invention is credited to David A. Bunger.
United States Patent |
4,031,795 |
Bunger |
June 28, 1977 |
**Please see images for:
( Certificate of Correction ) ** |
Tone signal modulation system
Abstract
Modulation systems for electrical signals representing music in
which synchronous vibrato and tremolo modulations are applied to a
flute signal in one channel, the vibrator being produced by a
bucket brigade modulator and the tremolo by a balanced modulator in
cascade with the bucket brigade modulator, and in which in a second
channel tones other than flute tones, and pedal tones, are
separately treated to have independent vibratos, and in which
balanced modulators for modifying the amplitude of the tone signals
are concurrently controlled by a common expression voltage. In one
modification flute signals are vibrato modulated in opposed phases,
and passed via diverse filters to a common tremolo modulator.
Provision is made for combining the inputs of the channels, the
outputs of which are electroacoustically transduced by separated
loudspeakers. Provision is made for slowly varying the frequency of
a sub-sonic modulating oscillator, which is either turned off, or
operates at about 1 or about 6 Hz., in proceeding from any one of
these three values to any other, the rate of variation being such
as to simulate the rate which occurs when the modulations are
produced by rotation of a mechanical device such as a rotating
loudspeaker.
Inventors: |
Bunger; David A. (Cincinnati,
OH) |
Assignee: |
D. H. Baldwin Company
(Cincinnati, OH)
|
Family
ID: |
24354636 |
Appl.
No.: |
05/588,627 |
Filed: |
June 20, 1975 |
Current U.S.
Class: |
84/705; 84/706;
984/308; 984/311 |
Current CPC
Class: |
G10H
1/0091 (20130101); G10H 1/043 (20130101); G10H
2210/215 (20130101); G10H 2210/251 (20130101); G10H
2210/281 (20130101) |
Current International
Class: |
G10H
1/00 (20060101); G10H 1/04 (20060101); G10H
1/043 (20060101); G10H 001/02 () |
Field of
Search: |
;84/1.01,1.24,1.25,DIG.4 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Weldon; Ulysses
Attorney, Agent or Firm: Kirkland & Ellis
Claims
What I claim is:
1. An electric organ system, comprising an electric organ having a
flute signal output lead and a heterosignal output lead, means
including a first analogue shift register means for modulating the
frequency of said flute signal, amplitude modulation means in
cascade with said analogue shift register, oscillator means
providing modulating signal to said analogue first shift register
means and to said amplitude modulator means, a first loudspeaker
responsive to the output of said amplitude modulator means, means
including a further analogue shift register for modulating the
frequency of said heterosignal, said heterosignal being exclusive
of said flute signal, a second loudspeaker connected in cascade
with said further analogue shift register, and switch means
operable for transferring signal from said heterosignal output lead
to the input of said first analogue shift register means, said
first and second loudspeakers being spatially separated
sufficiently to represent distinct acoustic sources.
2. The combination according to claim 1, wherein said first
analogue shift register means includes first and second analogue
shift registers connected in parallel to said flute signal output
lead, and said oscillator means comprises separate clock sources
connected respectively to drive said first and second analogue
shift register means, said clock sources being oscillators, and
means for driving said oscillators in opposite phases.
3. The combination according to claim 2, wherein said means for
driving said oscillators in opposite phases comprises a low
frequency voltage-controlled oscillator and an inverter.
4. The combination according to claim 2, further comprising first
and second diverse audio filters in cascade with said first and
second analogue shift registers respectively, said diverse filters
having diverse frequency cut-off ranges.
5. The combination according to claim 4 wherein said first diverse
audio filter has a cut-off range of approximately 20 Hz to 10 KHz
and said second diverse audio filter has a cut-off range of
approximately 1 KHz to 10 KHz.
6. The combination according to claim 1, wherein are provided
diverse modulating frequency sources for said first analogue shift
register means and said further analogue shift register.
7. The combination according to claim 1, wherein is provided means
for modifying the frequency of said modulating signal.
8. The combination according to claim 1, wherein is provided a
rotating speaker inertial simulator for modifying the frequency of
said modulating signal.
9. The combination according to claim 1, wherein is provided means
for slowly modifying the frequency of said sub-sonic oscillator at
a rate simulating the rate at which a mechanically rotated
loudspeaker varies.
10. In an organ system, sources of diverse frequency spectra,
separate frequency modulators for diversely frequency modulating
said diverse frequency spectra, means for amplitude modulating one
of said spectra in synchronism with the frequency modulation of
that one of said spectra, separated loudspeakers for
electro-acoustically separatedly transducing said spectra following
modulations thereof, and switch means for selectively combining
said frequency spectra at the input of one of said frequency
modulators, said frequency modulators including separate analogue
shift register means.
11. The combination according to claim 10, wherein one of said
analogue shift register means includes two analogue shift registers
having separate and independent clocks, and means for periodically
varying the frequencies of said clocks in substantially opposite
phases.
Description
BACKGROUND OF THE INVENTION
It is common in transducing electronic music to employ a rotating
loudspeaker, or a stationary loudspeaker and a moving horn or
reflector, to produce a rotating acoustic radiation pattern, the
rotation rate being about 6. or 7. rps., or less, and the motion
being such as to develop Doppler variations in frequency. Such
devices provide pleasing effects, the tones being both frequency
and amplitude modulated. In such systems, it is common to provide
variations in frequency of rotation. However, the cost of a
mechanical system is considerable in relation to the cost of a
common electronic organ.
It is an object of the present invention to provide a wholly
electronic system for simulating the audio effects produced by a
mechanically rotating acoustic source which is designed to produce
Doppler variations in frequency.
It is another object of the invention to provide a system in which
(1) flute and (2) other output tones, of an electronic organ, are
independently modulated in frequency and amplitude and radiated via
separate spatially separated loudspeakers.
The system employs cascaded frequency modulators and amplitude
modulators, the latter controlling expression and also introducing
tremolo.
SUMMARY OF THE INVENTION
An electric organ system, in which diverse tone source outputs are
diversely frequency modulated by means of analogue shift registers,
in separate channels, the content of one of the channels being
amplitude modulated at the same frequency as its frequency
modulation, the one of the channels containing selectively only
flute tone signals or a combination of flute and other tone
signals, and radiating the modulated tone content of the channels
via spatially separated loudspeakers.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of a first embodiment of the
invention;
FIG. 2 is a block diagram of a second embodiment of the invention;
and
FIG. 3 is a schematic circuit diagram of a circuit for slowly
varying the frequency of a modulating oscillator, responsive to
operation of a switch, in the systems of FIG. 1 or 2.
DESCRIPTION OF THE INVENTION
Referring now particularly to FIG. 1 of the drawings, the flute
tones of an organ 10 are applied via pre-amplifier 10a to a first
bucket brigade line or analogue shift register 11. The character
and function of register 11 is generally well understood. It is
driven in two phases .phi..sub.1, .phi..sub.2 by a 90. KHz. clock
12, which is a voltage controlled oscillator (VCO). The register
provides a nominal delay of 1.03 ms. If the VCO frequency is
modulated at a slow rate, the output of the shift register will be
delay modulated, delay time being inversely proportional to clock
frequency. This is equivalent to producing a varying frequency
shift since read-out is at times a different rate than read-in. It
is known that a bucket brigade delay line provides equal percentage
frequency shifts for all frequencies of input. If the rate of
change of delay with respect to time is varied in a sinusoidal
manner, in the present case either at a 6.4 Hz. or a 1 Hz. rate,
the output of the delay line will be frequency modulated at the
same rates. At the 6.4 Hz. modulation rate frequency modulation is
approximately 2.5% and at 1 Hz. about 0.5%.
The flute audio signal at the output of the shift register 11
contains the clock pulses. These are removed by low pass filter 13,
leaving the flute signal, and the latter is applied to a balanced
modulator amplifier 14, which introduces amplitude modulation. The
output of balanced modulator amplifier 14 is passed through a
conventional reverberator 15 and power amplifier 16 to a
loudspeaker 17.
The frequency of VCO 12 is controlled by a low frequency voltage
controlled oscillator 18, providing either 6.4 Hz. or 1 Hz. or zero
output, the latter output results in no frequency modulation of
clock 12, so that shift register 11 introduces a fixed delay of
1.03 ms.
The output of oscillator 18 is applied to balanced modulator 14,
and introduces amplitude modulation. The balanced character of
modulator amplifier 14 assures that the modulation frequency will
be suppressed and the signal passed through.
The balanced modulator 14 is also subject to a dc voltage, via line
19, from an expression pedal controlled potentiometer, so that the
volume of acoustic output can be controlled, as is conventional, by
an expression shoe.
The oscillator 18 is controlled in frequency by switch 20, and may
be turned on or off by switch 21, the switches 20, 21 setting a
control voltage to oscillator 18, via speed control circuit 22,
i.e., operation of the switches causes speed control 22 to provide
to oscillator 18 the requisite control voltage.
The output of pre-amplifier 10a is applied via lead 25 to a second
analogue shift register 26, of the bucket brigade type, driven by a
clock in the form of a two phase VCO 27. The latter is driven by
low frequency VCO 18 via phase inverter 28. The shift registers 11
and 26 are driven by different clocks, which deviate in frequency
in opposed phases. At the 6.4 Hz. modulation rate, frequency
modulation is approximately 4.0% and at 1 Hz. about 0.6%.
The output of shift register 26 is applied to balanced modulator 14
as an input signal via a band pass filter 29, having a band pass of
1-10 KHz.
The utilization of two frequency modulated versions of the flute
signal produces a more realistic tremolo effect than is true for a
single version. The diverse filters employed, i.e., low pass filter
13, cutting off at 10. KHz., and band pass filter 29, having a pass
band of 1-10 KHz., implies that for frequency below 1 KHz. shift
register 11 will provide the predominant audio signal to modulator
14, while for frequencies above 1 KHz. shift register 26 will
provide an additional audio signal to modulator 14. These are
identically amplitude modulated but diversely frequency modulated,
but in a controlled and not a random fashion. The summing of
outputs of shift registers 11 and 26, in addition to providing dual
frequency modulated outputs, causes a complex pattern of amplitude
modulation which is independent of the amplitude modulation
imparted to the signal by balanced modulator 14.
The output of organ 10, apart from flute signals, proceeds via line
30 to a pre-amplifier 31. The latter signal is applied to a third
analogue shift register 32 of the bucket brigade type. The latter
is driven by a clock 33 in the form of a two phase VCO, which is in
turn frequency modulated by a low frequency oscillator 34, via a
potentiometer 35 which controls the frequency deviation of the
clock 33. The output of shift register 32 is filtered by low pass
filter 36, to remove clock pulse frequencies, and applied to
balanced modulator 37. The latter is the same circuit as modulator
amplifier 14, except in that no amplitude modulation is applied,
but only expression control voltage via lead 38, so that flutes and
other tones will sound at the same audio levels.
The output of a pedal tone pre-amplifier 39 is applied to balanced
modulator amplifier 40 controlled from lead 38. The output of
modulator amplifier 37 is applied via reverberator 41 and power
amplifier 42 to loudspeaker 43, while the pedal signals are
amplified by power amplifier 44 to loudspeaker 45.
A switch 50, including ganged contacts 51 and 52, serves to control
the VCO 34 to a frequency of about 5.0 Hz. when the contacts 52 are
closed, and to about 6.4 Hz. when open and to convey signals from
pre-amplifier 31 to a pre-amplifier 10a when contacts 51 are
closed.
With switch 50 in closed condition, then, the shift registers 11
and 26 and the amplitude modulator 14 serve to modulate all tone
signals of the organ, as called for by appropriate stops. At the
same time tone signals other than flutes are vibrato modulated, and
heard via loudspeaker 43, and are frequency modulated at a
different rate with respect to those signals provided by
pre-amplifier 10a, but are not amplitude modulated.
The net response of the organ represents an augmented chorus
effect, the signal input via lead 30 being subject to many diverse
effects, i.e., to two out-of-phase frequency modulations in channel
A, to amplitude modulation in channel A, to diverse filtering in
channel A, to frequency modulation in channel B, and to radiation
via spatially separated loudspeakers for channels A and B.
FIG. 2 represents a simplified version of the system of FIG. 1.
Corresponding circuit elements are identified by corresponding
reference numerals in FIGS. 1 and 2. In FIG. 2 appears a switch 60,
having contacts 61 and 62. When contacts 62 are closed VCO 34 is at
5.0 Hz. When open, VCO 34 provides modulating signal at 6.4 Hz.
When contact 61 is closed the signal output of the organ 10,
exclusive of flute tones, is applied to the input of shift register
11, via lead 63.
Pedal frequencies are applied as signal input to modulator
amplifier 37, which is employed solely to control amplitude in
response to dc voltage provided via lead 64 from expression pedal
control source P.
The VCO 18 is, in FIG. 2, controlled by a voltage which varies
slowly. For example, if switch contact 65 is moved from its slow
contact 66 to its fast contact 67, the frequency output of VCO 18
is desired to change slowly from 1 Hz. to 6.4 Hz., and vice versa.
The rate of increase of frequency output of VCO 18 is controlled by
inertial simulator 68, which is designed to introduce a gradual
change of voltage simulating that which occurs when an attempt is
made to modify the speed of a mechanically rotating device.
The hetero signal may, if desired, include flute signals.
In the system of FIG. 2 is provided an inertial simulator IS, which
effects controlled slow variations of frequency of VCO 18.
Referring to FIG. 3 a dc voltage V.sub.r is developed at the
junction of diodes D.sub.4 and D.sub.5 which controls the frequency
of the low frequency voltage controlled oscillator (VCO). The
purpose of the inertial simulator circuit is to provide three
voltages which will cause the VCO 18 to simulate mechanical rotor
off, slow and fast conditions and to cause the voltage to change
from one value to the next in a controlled manner, causing the
frequency to change in such a way as to simulate the inertial
characteristics of a rotating speaker during speed-up and
slow-down. This effect is inherent in a rotating loudspeaker.
When the tremolo switch is "off" transistors Q19, Q17 and Q16 will
be off and no voltage will be developed at the anode of diode D5,
and no voltage will appear at the anode of diode D4. Thus, 0 volts
appears at the junction of D4 and D5 and the VCO 18 will not
oscillate, simulating the tremolo "off" conditions.
With the tremolo switch 21 "on" "slow" transistor Q19 will remain
off; however, +27 volts is applied to resistor R 140. Resistor RS35
is selected for a value of voltage at the anode of diode D4 which
will cause the VCO 18 to oscillate at 1 Hz. This voltage is also
applied to the base of transistor Q17 via diode D6 and causes a
voltage to appear at the anode of diode D5, which is three diode
drops below the voltage appearing at the anode of diode D4. Thus,
diode D5 is reversed biased. The purpose of diode D6 is to reduce
any time delay when switching from "slow" to "fast". This is
accomplished by the fact that capacitor C14 does not have to change
from ground but from a diode drop below the voltage appearing at
the anode of diode D4, thus reducing the time necessary for the
voltage at the anode of D5 to exceed the voltage at the anode of
D4, causing the frequency of the VCO 18 to start increasing.
With the tremolo switch "on" and "fast", transistor Q19 turns on,
charging capacitor C14 via R46 and D7. The rate of charge is
determined by the value of R46. The time necessary for C14 to
become fully charged is approximately 6 seconds. During this
charging time the rate of the VCO is increasing.
The voltage on C14 is applied via transistors Q17 and Q16 to the
anode of diode D5. Resistor Rs38 is selected by a value of voltage
at the anode of D5 which will cause the VCO 18 to oscillate at 6.4
Hz. Diode D4 is now reversed biased, thus the load of resistors
R140, R36 and Rs35 will not effect the voltage at the anode of
diode D5. Thus, diodes D4 and D5 are used to isolate any loading or
interaction between the "slow" and "fast" calibrating circuits.
When the tremolo switch is switched from "fast" to "slow"
transistor Q19 again turns "off" and no voltage is supplied to
capacitor C14 via diode D7. Transistor Q18 is turned on and
capacitor C14 is discharged via Q18 and resistor R43 at a rate
which is determined by the voltage at the base of Q18. C14 will
discharge until its voltage is a diode drop below the voltage at
the anode of D4 at which time D6 will become forward biased,
holding the voltage across C14 as previously described. The time
necessary for C14 to discharge is approximately 3 seconds.
Transistors Q16 and Q17 isolate the resistor load of R37, R39 and
Rs38 from capacitor C14 so the primary discharge path of C14 is via
transistor Q18. When switching from tremolo "fast" to "off"
transistor Q18 will not turn on. In this condition C14's primary
discharge path is via R42, collector base diode of Q19, resistor
R48, R45, R44 to ground. The time necessary for C14 to discharge to
ground via this path is approximately 7 seconds.
* * * * *